Heat exchangers performing heat exchange between two fluids, for example a gas and a liquid, have been known to use porous foamed metal fins to augment the heat transfer area to volume ratio on the gas side of the heat exchanger. Such fins are usually molded by solidifying molten metal in separate molds or directly in cavities formed by rigid components of the heat exchanger. It is also known, particularly in heat sinks, to obtain a foam metal heat dissipating structure by sintering metal particles directly in cavities formed by rigid components of the heat sink. In both cases, the heat exchanger or heat sink usually has a rigid structure which cannot be easily manipulated to conform to a desired shape.
Heat exchangers in a gas turbine engine need to occupy a minimal volume and include conduits with a small cross-section which can resist considerably high temperatures and pressures while remaining lightweight. Spiral heat exchangers are known to occupy a minimal volume and are usually formed by rolling two long sheets of metal around a common axis. However, maintaining a small gap between adjacent layers of the spiral to obtain small cross-section conduits is usually very complex. In addition, such rollable spaced apart sheets of metals are usually not adapted to resist to considerably high pressures.
Known heat exchangers having high temperature and pressure capabilities include superposed, parallel rigid plates connected by intermediate walls. However, such a construction, while strong, is usually difficult to adapt to a spiral geometry in order to make most effective use of the space occupied by the heat exchanger.
Accordingly, there is a need to provide an improved heat exchanger which can be easily formed into a desired shape.